The goal of this continuation project, submitted in response to PA-10-009 (Bioengineering Research Grants), is to develop new technology and to generate new knowledge that will accelerate the development of implants and surgical approaches to treat presbyopia. The project addresses two critical barriers: a) the need for instruments and techniques that measure the accommodative response and are suitable for clinical and objective evaluation of techniques to restore accommodation and b) the need to advance our understanding of the causes of presbyopia and discover the most effective strategies for restoration of accommodation. The project has three specific aims: Aim 1: To develop technology to simultaneously quantify the optical and mechanical in vivo accommodative response of the human eye. Optical coherence tomography systems, a dynamic aberrometer, an accommodation stimulus, and image processing software will be developed and integrated into a combined imaging and biometry system that will allow simultaneous measurement of the axial eye length, lens shape, lens internal structure, ciliary muscle geometry, and ocular refraction and aberrations in response to monocular accommodative stimuli. Aim 2: To characterize the age-dependence of the optical and anatomical changes in the lens and ciliary muscle with accommodation. The system developed in Aim 1 will be used to characterize the age-dependence of the accommodation-induced dynamic changes in outer and nuclear lens curvature; lens thickness and power; nuclear thickness and power; and ciliary muscle geometry. Data will be acquired on 200 human subjects from age 16 to 66. The results will be used to quantify the contribution of the lens and ciliary muscle to the loss of accommodation with age. Aim 3: To compare the pseudophakic accommodative response in subjects implanted with standard and accommodating intraocular lenses. The system developed in Aim 1 will be used to measure and compare the accommodation-induced changes in ciliary muscle geometry, intraocular lens position and ocular refraction in subjects implanted with standard monofocal intraocular lenses and subjects implanted with accommodating intraocular lenses. The results will be used to identify the parameters that govern near visual function in subjects with intraocular lenses. The project will have a broad impact on the field of presbyopia research. It will produce new technology to quantify the ocular accommodative response and evaluate the efficacy of procedures to restore accommodation. It will generate new knowledge on the causes of presbyopia and identify parameters that govern near-visual function in eyes with intraocular lenses. The knowledge gained will form a sound physiological basis for the development and optimization of new procedures and implants designed to restore accommodation.